A conventional body structure for a rail-car, for example, a side structure, is manufactured by weld-joining a rocker rail, a side post, a belt rail, a window head, a window post, a door end post and so on.
Since the car-body structure is composed of many frame members, a frame formed in a one-piece structure is proposed in order to simplify the car-body structure.
In a car-body structure disclosed, for example, in Japanese Patent Application Laid-Open No.5-262228, a frame member is formed of corrugated plates divided into a plurality of sections and having a plurality of ribs, and the frame member is spot-welded to an outside plate. The frame member has holes on a surface in contact with the outside plate. Further, reinforcing members are welded and joined to the corrugated plates in a direction transversely intersecting with the corrugated plates.
In a car-body structure disclosed in Japanese Patent Application Laid-Open No.5-262227, ribs in the car-body structure according to the patent application are arranged so as to be staggered.
Further, in a car-body structure disclosed in Japanese Patent Application Laid-Open No.5-69823, a side structure is formed by joining a plurality of inner panels having projections and depressions formed by press working to a flat-plate outer panel to be used as an outside plate.
However, the above-mentioned car-body structures in, there is problem in that strain occurs and dimensional accuracy is degraded due to use of many kinds of members, a large number of parts and weld-joining of individual frame members.
Since the car-body structure disclosed in Japanese Patent Application Laid-Open No.5-262227 has a great number of long ribs in the longitudinal direction of the car-body, the stiffness of the car-body structure in the vertical direction is low. Therefore, additional posts are provided. Notches are provided in order to prevent the occurrence of wrinkles or cracks around a hole, which makes the manufacture complex.
In addition to this, since the reinforcing plate in each of the above cited references is fabricated by press working, strain is apt to occur and the surface flatness is degraded. When such a reinforcing plate is spot-welded to an outside plate, strain or unevenness occurs in the outside plate. Therefore, the dimensional accuracy is degraded, and, consequently, the assembling accuracy of the car-body is degraded.
The objective workpiece in each of, Japanese Patent Application Laid-Open No.5-262227, Japanese Patent Application Laid-Open No.5-262228 and Japanese Patent Application Laid-Open No.5-69823, has a side structure without a bending portion in a wainscot panel portion of the car-body. Therefore, the technology disclosed in each of the above-mentioned publication cannot be applied to a car-body having a bending portion in a wainscot panel portion of the car-body.